US4014813A - Hafnium pyrophosphate phosphors and methods of preparation - Google Patents

Hafnium pyrophosphate phosphors and methods of preparation Download PDF

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US4014813A
US4014813A US05/539,906 US53990675A US4014813A US 4014813 A US4014813 A US 4014813A US 53990675 A US53990675 A US 53990675A US 4014813 A US4014813 A US 4014813A
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hafnium
mixture
luminescent material
compound
zirconium
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Igal Shidlovsky
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RCA Licensing Corp
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Priority to DE2503553A priority patent/DE2503553C2/de
Priority to CA219,076A priority patent/CA1055246A/en
Priority to SE7501089A priority patent/SE402466B/xx
Priority to FR7503213A priority patent/FR2259788B1/fr
Priority to JP50014773A priority patent/JPS5148469B2/ja
Priority to SU752104683A priority patent/SU645594A3/ru
Priority to CH129375A priority patent/CH608030A5/xx
Priority to NL7501306A priority patent/NL7501306A/
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Assigned to RCA LICENSING CORPORATION, TWO INDEPENDENCE WAY, PRINCETON, NJ 08540, A CORP. OF DE reassignment RCA LICENSING CORPORATION, TWO INDEPENDENCE WAY, PRINCETON, NJ 08540, A CORP. OF DE ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: RCA CORPORATION, A CORP. OF DE
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B25/00—Phosphorus; Compounds thereof
    • C01B25/16—Oxyacids of phosphorus; Salts thereof
    • C01B25/26—Phosphates
    • C01B25/38—Condensed phosphates
    • C01B25/42—Pyrophosphates
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
    • C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
    • C09K11/70—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing phosphorus

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  • This invention relates to novel ultraviolet-emitting phosphors and to methods of preparation thereof.
  • inorganic cathodoluminescent materials which can emit at wavelengths below 3000 A, and very few such phosphors are known.
  • One such phosphor disclosed in U.S. Pat. No. 2,770,749 to A, Bril et al., is a self-activated zirconium pyrophosphate phosphor (ZrP 2 O 7 ). This phosphor contains highly-charged zirconium ions with an np 6 nd 0 configuration. The emission is believed to come from the metal ions themselves, through charge transfer transitions between the O 2 - anions and the central metal ion. No activators are needed for this process.
  • the novel phosphors herein consist essentially of hafnium pyrophosphate wherein 0 to 20 mole percent of the hafnium is substituted with at least one of zirconium, germanium and silicon.
  • the unsubstituted species may be represented by the molecular formula HfP 2 O 7 .
  • the phosphors are prepared by heating in air at temperatures of about 1000° to 1300° C mixtures of a hafnium compound and a phosphate for a period of at least 30 minutes. No additional ions are required to activate the phosphor.
  • the novel phosphors are roentgenoluminescent, cathodoluminescent and photoluminescent, emitting in broad spectral bands which peak at about 2600 to 3000 A.
  • the novel phosphors may be used for their ultraviolet emission; for example, in cathode-ray display tubes, flying spot scanners, or in any of the applications mentioned in the above-cited patent to Bril et al.
  • FIG. 1 is a family of curves comparing the cathodoluminescent emissions of novel hafnium pyrophosphate phosphors made from a mixture having a stoichiometric ratio of hafnium and phosphate (curve 21), a mixture having an excess of phosphate (curve 23), and a mixture having an excess of hafnium (curve 25), and the emission from a zirconium pyrophosphate phosphor prepared from a stoichiometric mixture (curve 27).
  • FIG. 2 is a curve showing the effect on power efficiency of substituting zirconium for up to 20 mole percent of the hafnium in HfP 2 O 7 .
  • Example 1 To prepare hafnium pyrophosphate phosphor from a stoichiometric mixture, mix 1.00 gram-molecular weight hydrated hafnium oxychloride HFOCl 2 .sup.. 8H 2 O with 2.00 gram-molecular weight ammonium dihydrogen phosphate NH 4 H 2 PO 4 . Place the mixture in an alumina container and heat the mixture in air at about 800° C for about 4 hours (preliminary firing), and cool to room temperature. Crush the material and reheat the mixture in an alumina container in air for about 4 hours at about 1200° C (main firing) and then cool to room temperature. The reheating cycle may be repeated to improve the uniformity in the product.
  • a small amount of HfO 2 appears in the x-ray pattern.
  • the product is roentgenoluminescent, photoluminescent and cathodoluminescent, emitting in the 2400 to 3400 A spectral range with a peak at about 2940 A. With cathode-ray excitation, the phosphor exhibits a power efficiency of about 8 percent.
  • a cathodoluminescent emission curve 21 for the hafnium pyrophosphate phosphor prepared by this example is shown in FIG. 1.
  • a similar curve 27 for a zirconium pyrophosphate phosphor made by a similar method, also shown in FIG. 1, is shifted about 100 A toward longer wavelengths.
  • Example 2 follows the procedure of Example 1 except substitute hafnium oxide HfO 2 for hydrated hafnium oxychloride. A similar product to that produced in Example 1 is produced.
  • Example 3 To prepare hafnium pyrophosphate phosphor from a mixture containing excess phosphate, follow the procedure of Example 1 except substitute 2.20 gram-molecular weight ammonium dihydrogen phosphate (instead of 2.00 gram-molecular weight).
  • the product is roentgeneoluminescent, photoluminescent and cathodoluminescent, emitting in the 2000 to 3000 A spectral range with a peak at about 2740 A. With cathode-ray excitation, the phosphor exhibits a power efficiency of about 2 percent.
  • a cathodoluminescent emission curve 23 for the HfP 2 O 7 phosphor prepared by this example is shown in FIG. 1.
  • Example 5 To prepare a stoichiometric HfP 2 O 7 by another method, place 10 grams of HfOCl 2 .sup.. 8H 2 O powder in a Teflon beaker and add concentrated phosphoric acid thereto. The amount of acid is just enough to wet all of the powder. That amount is in excess to the stoichiometric amount which is needed to convert all the oxychloride to pyrophosphate. Heat the mixture on a hot plate with stirring for about six hours in order to produce a thick slurry. Transfer the slurry to a silica container.
  • the container and slurry in a furnace in air for about 4 hours at 400° C, then for about 6 hours at 800° C and then for about 4 hours at 1000° C.
  • the resultant material is cooled, crushed and ground.
  • the ground material is reheated in a silica container at about 1200° C for about 6 hours in air.
  • the reaction product is a powder consisting essentially of cubic hafnium pyrophosphate. Cathodoluminescence measurements of the material prepared by this example showed that the material emits in a broad band which peaks at about 2920 A with a power efficiency of 9.6%.
  • Example 6 follows the procedure in Example 5 except substitute a mixture of P 2 O 5 and water for the phosphoric acid.
  • the resulting product is similar to the one described in Example 5.
  • the novel phosphor may be prepared by a variety of procedures.
  • a hafnium compound is reacted with a phosphate compound.
  • Any hafnium compound such as hafnium oxide or hafnium oxychloride, may be used.
  • Any phosphate such as ammonium phosphate, ammonium dihydrogen phosphate, sodium pyrophosphate, or potassium dihydrogen phosphate may be used. Water-soluble phosphates of light cations are preferred.
  • hafnium and phosphate ions no other ions are neccessary. Cations which degrade the luminescence in the product, particularly cations of the heavy metals, should be avoided.
  • the materials should be thoroughly mixed, and then given a preliminary firing to reduce the volatilization of phosphate during the main firing. Then, the mixture is reheated in air at temperatures between 1000° and 1300° C, preferably 1150° to 1250° C, for any convenient length of time greater than about 30 minutes, and then cooled to room temperature.
  • the reheating (main firing) cycle may be repeated as many times as is desired in order to improve the uniformity of the product.
  • the emission peak of the product may be shifted, as disclosed in the examples, by including controlled proportions of hafnium and/or phosphate in the reheating (main firing) cycle.
  • the starting mixture may be mixed as dry powders, but is preferably mixed with an excess of water, which is later evaporated. The wet mixing helps to obtain a more homogeneous mixture. After the water is evaporated from the slurry, the remaining solid is ready for heat treatment. Following heat treatment, the reaction product may be washed to remove any water-soluble material that is present.
  • a hafnium compound is reacted with phosphoric acid or P 2 O 5 and water.
  • the second method yields pure hafnium pyrophosphate that is substantially free of residual oxide. Residual oxide is always present as a second phase together with the pyrophosphates when the novel phosphors are prepared by the foregoing first method.
  • the synthesis is done by reacting hafnium oxychloride and phosphoric acid (or a solution of P 2 O 5 and water). A mixture of hafnium oxychloride and phosphoric acid is first heated while stirring in a Teflon container on a hot plate. Then the mixture is transferred to a silica container.
  • the container and contents are heated gradually to 1000° C.
  • the temperature of the container is raised to 400° , then to 800° , and then to 1000° C, soaking the contents for a few hours at each of the mentioned temperatures.
  • the material is cooled to room temperature, crushed and ground. Then, the ground material is heated in air at 1200° C.
  • FIG. 1 shows the cathodoluminescent emission spectra of HfP 2 O 7 and ZrP 2 O 7 phosphors made from stoichiometric mixtures in curves 21 and 27 respectively, as was obtained from samples prepared by the procedure of Example 1.
  • the intensity scale in the Figure is arbitrary and does not represent the comparable emission intensity between the phosphors.
  • the HfP 2 O 7 phosphor peaks at about 2940 A and the ZrP 2 O 7 phosphor peaks about 100 A higher. Power efficiency measurements show that the HfP 2 O 7 phosphor exhibits, under cathode-ray excitation, about twice the efficiency of a similar ZrP 2 O 7 phosphor.
  • the cathodoluminescent emissions from HfP 2 O 7 phosphors that were prepared by us have varied somewhat. All of the samples made emit in broad bands that peak in the range from about 2950 A to about 2660 A.
  • the emission spectra for the two extreme emissions of HfP 2 O 7 phosphors are plotted on FIG. 1 with the curves 21 and 25. The plot is of the luminescence intensity in arbitrary units against the wavelength in angstroms. The relative intensity between the two emission curves is not maintained in FIG. 1.
  • the power efficiency for the 2940 A peak emission is about 8 percent and about 1.5 percent for the 2660 A peak emission.
  • the photoluminescence at room temperature has been studied. Excitation with 1900 A radiation causes emission in the ultraviolet region, at about the same wavelengths as the cathodoluminescence. This absorption is assumed to be part of the band edge which tails to lower energies due to internal defects. Precise measurements of the fundamental and actual band edge in the material are not available. Two more absorption bands are observed at 2200 A and 2300 A. The 2200 A absorption is connected with the ultraviolet emission and the 2300 A with visible emission. The visible emission is very weak in comparison to the ultraviolet emission.
  • the wavelengths of the emission band may be somewhat variable. Emission bands that peak at longer wavelengths are somewhat more efficient than emission bands at shorter wavelengths. The efficiency and the emitted energy are correlated together with the amount and nature of internal defects in the material. Generally, when more defects are present in the material, the power efficiency of the luminescence is higher, but the emitted radiation is at longer wavelength (lower energy).
  • Impurities which are introduced into the starting mixture have a large influence on the cathodoluminescent power efficiency of the product.
  • Substituting one or more of silicon, germanium and zirconium for a portion of the hafnium in hafnium pyrophosphate increases significantly the efficiency of cathodoluminescence of the product. Measurements have been done with materials which contain up to 20 mole percent zirconium in the hafnium pyrophosphate as shown by the curve in FIG. 2. The most efficient phosphor found in this series is one containing around 0.5 mole percent of zirconium.
  • Zirconium-substituted hafnium pyrophosphate may be prepared in a similar way to the preparation described above except that a zirconium compound substitutes for a portion of the hafnium compound. For example, mix 0.5 mole percent zirconium oxychloride with 99.5 mole percent hafnium oxychloride and add phosphoric acid. Then, proceed as in Example 5. A hafnium pyrophosphate with 0.5 percent zirconium prepared by this method was measured to emit with 11 percent power efficiency under cathode-ray excitation. The emission is in a broad band which peaks at around 2910 A.
  • Silicon- or germanium-substituted hafnium pyrophosphate may be prepared by the method of Example 5 except that silicon dioxide SiO 2 or germanium dioxide GeO 2 is substituted for a portion of the hafnium compound.
  • the SiO 2 or GeO 2 is first added to hot concentrated phosphoric acid, and after the oxide reacts with the acid, the hafnium oxychloride is added. The rest of the preparation is the same as described in Example 5 with silicon- or germanium-substituted hafnium pyrophosphates.
  • the best efficiency is achieved with around 1 mole percent of substituent. Power efficiencies were measured to be over 10 percent, and emission peaks were measured at around 2910 A. The power efficiencies were more than 10 percent higher than unsubstituted zirconium pyrophosphates. Materials prepared by Example 5, although not intentionally doped, have substantial amounts of silicon and germanium. Silicon is introduced mainly from the container. The phosphoric acid contains also silicon and germanium. The best power efficiency achieved from an unsubstituted sample, which was prepared from the oxides, or oxychloride and ammonium dihydrogen phosphate as by the procedure of Example 1, was measured as 8 percent.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Luminescent Compositions (AREA)
US05/539,906 1974-02-04 1975-01-13 Hafnium pyrophosphate phosphors and methods of preparation Expired - Lifetime US4014813A (en)

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Application Number Priority Date Filing Date Title
US05/539,906 US4014813A (en) 1974-02-04 1975-01-13 Hafnium pyrophosphate phosphors and methods of preparation
DE2503553A DE2503553C2 (de) 1974-02-04 1975-01-29 Verwendung von Hafniumpyrophosphat
CA219,076A CA1055246A (en) 1974-02-04 1975-01-30 Hafnium pyrophosphate phosphors and methods of preparation
SE7501089A SE402466B (sv) 1974-02-04 1975-01-31 Luminescent material
FR7503213A FR2259788B1 (ja) 1974-02-04 1975-02-03
JP50014773A JPS5148469B2 (ja) 1974-02-04 1975-02-03
SU752104683A SU645594A3 (ru) 1974-02-04 1975-02-03 Люминесцентный материал
CH129375A CH608030A5 (ja) 1974-02-04 1975-02-04
NL7501306A NL7501306A (nl) 1974-02-04 1975-02-04 Werkwijze ter bereiding van ultraviolet-emit- de fosforen.

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US05/539,906 US4014813A (en) 1974-02-04 1975-01-13 Hafnium pyrophosphate phosphors and methods of preparation

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4068128A (en) * 1976-12-30 1978-01-10 Gte Sylvania Incorporated (Hf1-x Zrx)3 P2 O11 luminescent material, method of preparation and X-ray intensifying screen containing same
US4395387A (en) * 1981-10-13 1983-07-26 Pennwalt Corporation Method for manufacturing water glass cement hardeners
US4414187A (en) * 1982-05-19 1983-11-08 The United States Of America As Represented By The United States Department Of Energy Preparation of metal phosphates by a reaction using boron phosphate
US5746943A (en) * 1997-02-25 1998-05-05 Sterling Diagnostic Imaging, Inc. X-ray intensifying screen based on barium hafnium zirconium phosphate
US20150262780A1 (en) * 2014-03-13 2015-09-17 Stellarray, Inc. UV Pipe

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3941715A (en) * 1975-03-24 1976-03-02 Rca Corporation Substituted zirconium pyrophosphate phosphors

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB680846A (en) * 1950-07-04 1952-10-15 Gen Electric Co Ltd Improvements in or relating to luminescent materials
US3351436A (en) * 1964-12-28 1967-11-07 Gen Electric Preparation of thorium pyrophosphate
US3642651A (en) * 1969-04-07 1972-02-15 Brockway Glass Co Inc Photoluminescent glass and method of making the same
US3814967A (en) * 1971-12-29 1974-06-04 Hitachi Ltd Luminescent screen for flying-spot cathode-ray tube

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US277049A (en) * 1883-05-08 Fire-escape

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB680846A (en) * 1950-07-04 1952-10-15 Gen Electric Co Ltd Improvements in or relating to luminescent materials
US3351436A (en) * 1964-12-28 1967-11-07 Gen Electric Preparation of thorium pyrophosphate
US3642651A (en) * 1969-04-07 1972-02-15 Brockway Glass Co Inc Photoluminescent glass and method of making the same
US3814967A (en) * 1971-12-29 1974-06-04 Hitachi Ltd Luminescent screen for flying-spot cathode-ray tube

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
Chemical Abstract, 3150a, (1954). *

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4068128A (en) * 1976-12-30 1978-01-10 Gte Sylvania Incorporated (Hf1-x Zrx)3 P2 O11 luminescent material, method of preparation and X-ray intensifying screen containing same
US4395387A (en) * 1981-10-13 1983-07-26 Pennwalt Corporation Method for manufacturing water glass cement hardeners
US4414187A (en) * 1982-05-19 1983-11-08 The United States Of America As Represented By The United States Department Of Energy Preparation of metal phosphates by a reaction using boron phosphate
US5746943A (en) * 1997-02-25 1998-05-05 Sterling Diagnostic Imaging, Inc. X-ray intensifying screen based on barium hafnium zirconium phosphate
EP0860492A1 (en) * 1997-02-25 1998-08-26 STERLING DIAGNOSTIC IMAGING, Inc. X-ray intensifying screen based on barium hafnium zirconium phosphate
US20150262780A1 (en) * 2014-03-13 2015-09-17 Stellarray, Inc. UV Pipe
US9242019B2 (en) * 2014-03-13 2016-01-26 Stellarray, Incorporated UV pipe

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JPS5148469B2 (ja) 1976-12-21
DE2503553C2 (de) 1984-05-17
NL7501306A (nl) 1975-08-06
SU645594A3 (ru) 1979-01-30
FR2259788A1 (ja) 1975-08-29
DE2503553A1 (de) 1975-08-14
SE402466B (sv) 1978-07-03
FR2259788B1 (ja) 1979-09-28
CH608030A5 (ja) 1978-12-15
CA1055246A (en) 1979-05-29
SE7501089L (ja) 1975-08-05
JPS50114390A (ja) 1975-09-08

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